The present invention relates to a personal authentication apparatus using a living body. More particularly, it relates to a biometric personal authentication apparatus based on the vein pattern of a finger.
In recent years, attention has been focused on biometric authentications as security schemes where carrying a key or the like is unnecessary, a high convenience is accomplished, and there is a less danger of being illegally exercised by being lost or stolen. In these biometric authentications, a part of the body of an individual person, such as fingerprint, iris, or vein pattern, is used as the key. Of these biometric authentications, in the authentication methods using the vein pattern of a finger, criminal investigation is not associated therewith, or, unlike the case of the iris, an eyeball is not directly illuminated with light. Accordingly, in the authentication methods using the finger-vein pattern, there exists an advantage of causing only a little sense of psychological resistance. Also, in the authentication methods using the finger-vein pattern, the authentication is based not on characteristics of the easily observable living-body surface, but on inner characteristics of the living body. Consequently, there also exists an advantage that there is no residual property, and that their forgery is difficult to implement.
As a conventional embodiment of the finger-vein authentications of this type, there has been known an authentication apparatus disclosed in, e.g., JP-A-2007-206991. Not being limited to this apparatus, in the finger-vein authentications, there has been known the following method: Namely, in order to image the vein pattern of a finger, the finger is illuminated with near-infrared light, then being seen through with the near-infrared light which has passed through the inside of the finger. Here, in general, hemoglobin in the blood which is flowing in the vein absorbs the near-infrared light. As a result, in the vein part, the light is weakened after transmitting there; whereas, in the other part, the light passes therethrough just as it is. Accordingly, the contrast between these lights forms the vein pattern. In particular in JP-A-2007-206991, the following scheme is disclosed: Namely, in order to image the vein pattern of the ball side of a finger, the near-infrared light is caused to enter the inside of the finger from a part of the ball side of the finger. Moreover, the vein pattern of the ball side is subjected to the transmission imaging, using the light which travels in the inside of the finger while being scattered there, and which appears onto the outside of the finger from a different part of the same ball side of the finger. The employment of this scheme allows a light source and a vein imaging camera to be united and integrated only at the finger's ball-side. As a result, an extra structure becomes unnecessary on the periphery of a part on which the finger should be placed in the authentication apparatus. Consequently, it has been found successful to implement the flat-plane-shaped and space-saving authentication apparatus.
Also, in JP-A-2004-265269, the disclosure has been made concerning the small-size implementation of a part in which the user is engaged at the time of the authentication, such as an open-type apparatus where light sources are positioned on both side-surfaces of the finger.